Electric heater.



N0. 635,|32. Patented Oct. I7, I899. E. E. GOLD.

ELECTRIC HEATER.

(Application filed May 18, 1898.) (No Model.)

FIG, 7.

WITNESSES; INVENTORZ 144 11 1 zwww AM By his Alzomeys,

AWE-

UN TED STATES PAIENT ELECTRlC HEATER.

SPECIFICATION forming part of Letters Patent No. 635,132, dated October1'7, 1899.

Original application filed January 31,1898, Serial No. 668,528, Dividedand this application filed May 18, 1898. Serial No. 681,012. (No model.)

To all whom, it may concern:

Be it known that I, EDWARD E. GOLD, a citi-- zen of the United States,residing in the city, county, and State of New York, have inventedcertain new and useful Improvements in Electrio Heaters, of which thefollowing is a specification.

This invention relates to electric heaters of that class in which theheat is generated by passing an electric current through a resistantwire which is exposed to the air and which are of that generalconstruction in which such wire is wound first into a helix or coil,which helix is then wound'or coiled helically around a support to form acompound helix.

My invention relates to the means for supporting such compound resistanthelix.

According to myinvention I provide a skeleton or open-work support inthe general form of a tube and adapted to afford free circulation of airthrough the compound resistant helix, which is wound on such support insuch manner that the latter is thoroughly ventilated and exposed asfully as possible to contact with the surrounding air, so as to beefficiently cooled thereby. Preferably this openwork support is made bycoiling a wire or rod of sufficient strength into a helix with openconvolutions spaced apart somewhat less than the diameter of theresistant helix, so that when the latter is coiled around the outside ofsaid helical support it rests in the spaces between the convolutionsthereof, so as to make exterior tangential contact therewith at twopoints in each loop or minor convolution of the resistant helix. Thehelical support ing-wire'is enameled or otherwise provided withheat-resisting insulation in order that the support shall insulate thesuccessive convolutions of the compound resistant helix from oneanother.

My present application is a division of my application, Serial No.668,528, filed January 31, 1898, that application having been in partdivisional of my application, Serial No. 655,176, filed October 1 1-,1897, in that claim 1 of the latter was transferred into it and is nowby the filing of this application transferred from said applicationSerial No. 668,528 into my present application, being claim 1 herein.

My present application is in part specific to said application SerialNo. 668,528.

Figure l of the accompanying drawings is a sectional elevation of aheater constructed according to my invention, being partly dissectedaway in vertical mid-section. Fig. 2 is a transverse section thereof.Fig. 3 is a sectional and partly-dissected elevation of a modifiedconstruction.

In the drawings let A designate a helix of resistant wire and let Bdesignate the openwork support therefor, constructed preferably, asshown in Figs. 1, 2, and 3, of a stiff wire wound into a helix andenameled. The resistant wire A is first wound into ahelix in any usualmanner as, for example, by winding it upon a mandrelthe helix thusformed being herein referred to as the minor helix. This minor helix isafterward coiled around the exterior of the helical support 13, thelarger helix thus formed being herein referred to as a major helix. Thewire thus coiled first into a minor helix and then into a major helixconstitutes a compound helix. The supporting-wire B is of sufficientsize to afford the requisite stiffness and is coiled into an open helixas by winding upon a mandrel of considerably larger diameter than thatused in winding the minor helix. lts successive convolutions are spacedapart between centers somewhat wider than the exterior diameter oftheminor helix A, to the end that when the resistant helix is wound aroundthe support its successive major convolutions shall be spaced apart toafford ample insulation. At the same time the space between theconvolutions of the helix B must be less than the exterior diameter ofthe minor helix A to prevent this helix falling into such space. The

' proportions shown are considered preferable,

since they afford ample support for the resistant helix and ampleseparation for the successive major convolutions thereof to atford therequisite insulation, while the convolutions of the supporting-helix aresufficiently separated to leave ample space between them for upwardcirculation of air in the manner indicated by the arrows. It will beseen that by this construction the resistant helix A is extendedparallel with the supporting-wire B, so that the latter forms acontinuous longitudinal support making contact with each successiveconvolution of the resistant helix. The resistant helix is at eachconvolution supported on two successive convolutions of the helix 13, sothat it rests thereagainst at two points,thereby maltingits support firmand stiff. As these points of contact are formed by the exteriortangential contact of circles, they are, in fact, mere geometricalpoints disposed longitudinally of the supporting-wire B at a distanceapart equal to the pitch of the minor helix A. It results from this thatwith the exception of these minute points the entire surface of theresistant wire of the helixA is out of contact with every other part andfully exposed to the air or other surrounding medium by which itsgenerated heat can be rapidly conducted away, so that this form ofheater at tains the ideal of free radiation, combined with a securesupport for the resistant wire. The entire heater is, in fact, askeleton having wide spaces through which the air may freely circulate,which spaces are crossed and subdivided at frequent intervals by the hotwires of the resistant helix, so that the air flowing through the heateris successively subdivided by these hot wires, and consequently iseffectively heated. The support is also of such construction as to havethe minimum of mass for a given degree of strength or rigidity, so thatthere is the least possible heat-absorptive property in the supportconsistent with its properly performing its supporting function. Itresults from this that the heater is highly efficient from the veryinstant when the electric current is turned on, since but a very smallproportion of the heat is absorbed in heating up the support, and byreason of the support being so thoroughly subdivided into such slenderelements as to expose a large radiating-surface it is capable of givingout the heat to the air almost as rapidly as of receiving it from theresistant wire, and hence it very quickly re ceives the maximum of heatwhich it is capable of retaining.

It is of course essential to insulate the re sistant wire A. from thesupportingwlire B. This might be done by coating either wire withinsulating material; but since to coat the wire A would obstruct theradiation of heat therefrom it is preferable to apply the insulation tothe supporting-wire B. This insulation must be of such character as tobe unaffected by the heat which is generated, and for this reason it ispreferable to employ a vitreous enamel. This is found highly successfulin practice, it being only necessary to employ an iron wire ofsufficient diameter, wind it into the helix desired, then dip it intoenamel, and fire this enamel on. he ends of the wire, however, arepreferably left uncoated in order that they may be screw-threaded forattaching the supporting-helix in the heater. The enamel coating islettered a a.

It is essential that the minor helix A shall be wound upon the helicalsupport with a contractile tension in order that this tension shallcause it to draw itself constantly into close and firm contact with thesupportingwire. To this end the resistant wire is wound closely upon itsmandrel, and in then winding it into a major helix around the support Bit is stretched as it is wound on, thereby opening or pulling apart itsminor convolutions. The tension should be sufficient to maintain theresistant wire firmly against the support notwithstanding its tendencyto expand when heated by the current and notwithstanding the extent towhich its tension will be weakened by such heat. No considerable degreeof tension need be allowed for, however, in view of theseconsiderations, since in my heater, owing tothe perfect ventilation, thewires are never permitted to become highly heated.

For supporting the helical support B, I have shown in Figs. 1 and 3 ahead or disk 0, preferably of porcelain, at each end of the heater, thetwo heads being held rigidly apart either by means of an exterior casingG, as shown in Fig. 1, or by a tie-rod D, as shown in 3, which rod maypass centrally through the heater within the axis of the helix B, itsends being screw threaded and having nuts cl screwed thereon to clampthe heads tightly upon the .rod. If the casing G is used, as shown inFig. 1, it may be held by its ends, slipping over bosses 0, formed onthe heads 0 (land entering its ends. The opposite ends of the helix l3are inserted through suitable holes in these heads and, beingscrew-threaded, have nuts 0 screwed thereon, whereby to draw them firmlyagainst the heads to take up any looseness or slack and also preferablyto slightly stretch the helix B to impart firmness and rigidity to itsconvolutions and in Fig. l to press the heads firmly against the ends ofthe casing G. The ends of the helix A are secured by being fastened tobinding posts or bolts E, of which one is shown, which pass throughholes in the heads, being secured by screwing a nut e on the outer end,to which post the circuit wire it may be clamped by the same nut or byan outer nut c.

I prefer to construct the heater with the outer casing G, which inclosesthe compound coil, as shown. This casing is made of enameled metal,preferably in the form of a foraminous or open-work tube, so as to admitfree passage of air; but any skeleton form of suitable strength willanswer. It is arranged substantially concentric with the compound coilwhich it incloses and is but slightly larger than the diameter of thiscoil in order that if the resistant wire should break, so as to releaseit from restraint, the consequent expansion or unwinding of the minorhelix in its endeavor to straighten out into its original form willalmost instantly be restrained by the casing, so that the severed wirescan do no harm. "With existing heaters when the formation of shortcircuits.

It will be understood that my invention provides a novel support for thecompound helix consisting of a hollowopen-work body in the general formof a hollow cylinder or tube, which permit-s free circulation of airthrough the central space inclosed within the major helix, so that airmay circulate freely through and across the convolutions of theresistant wire. By this means the convolutions of wire extending alongthe top of the support do not become overheated, as in the case of asolid cylindrical support.

The open-work or skeleton tubular support may be constructed otherwisethan by coiling a supporting-wire into a helix. One suitablemodification thereof consists in making it of a foraminous tube, asshown in my said application, Serial No. 655,176, filed October 1 L,1807. It made of metal, it should be coated with insulating enamel.

I claim as my invention the tollowing defined novel features,substantially as hereinbefore specified, namely:

1. An electric heater comprising a skeleton or open-work support in thegeneral form of a tube, and a helix of resistant wire wound helicallyaround said support, whereby air may circulate between the meshes ofsaid helix and through the openings into and out of the interior of saidsupport, and into con tact with all portions of the heated resistantwire.

2. An electric heater comprising a skeleton support in the general formof a tube, consisting of a supporting-wire coiled into an open helix,and a helix of resistant wire coiled into a'compound helix around theoutside of said supporting-helix and resting in the spaces between theconvolutions thereof so as to make tangential contact therewith at twopoints in each minor convolution.

An electric heater comprising a supporting-helix B with openconvolutions, and a re= sistant helix A wound distensively into acompound helix around the outside of said helix B, so that it rests inthe spaces between adjacent convolutions thereof, and has a contractiletension drawing it into firm tangen tial contact therewith.

at. An electric heater comprising a compound helix of resistant wire, aninternal support around which said, helix is wound, and an outerinclosing casing G consisting of an open-work tube of enameled metal,whereby in case of breakage of the resistant wire the unwinding thereofwould be restrained by the casing, and short-circuiting and arcingprevented.

In witness whereof I have hereunto signed my name in the presence of twosubscribing witnesses.

EDXVARD E. GOLD.

Vitnesses:

FRED WHITE, THOMAS F. WALLAOE.

